Refrigeration is essential to maintaining freshness of crops and other perishable goods. As with any refrigeration units, frost build-up can reduce the efficiency of refrigeration units. As refrigeration units are opened and closed during normal use, water vapor from ambient air enters the refrigerator, condenses, and eventually freezes. The frost inhibits heat transfer into and out of the refrigeration unit, lowering efficiency. The frost can also accumulate on the refrigerated goods and damage them. In the extreme case, excessive moisture accumulation can reduce the efficiency to such a degree that the refrigeration unit is inoperable. Defrosting a refrigeration unit, however, can be difficult and inconvenient. One approach is to empty the unit and let ambient air melt the frost. This, however, requires that the goods be moved and stored while the frost melts. An alternative method is to melt the frost without removing the goods from the unit, but this process must be fast enough that the goods are not harmed by the heat applied to melt the frost. An improved defrost cycle can improve the efficiency of a refrigeration unit and thus the profitability of an enterprise.